This invention relates to a trimmer device for the tobacco filler in a cigarette manufacturing machine. In cigarette manufacturing machines of the continuous rod type, a tobacco filler or layer is formed by accumulating individual particles of tobacco on a support constituted by a conveyor belt driven with continuous motion.
During its transfer by said belt to the means for forming the individual cigarettes, the tobacco filler is subjected to a so-called trimming operation, the purpose of which is to make it substantially constant in height or thickness.
The means used for this purpose, known as trimmers, are frequently constituted (see for example British Pat. No. 881,024) by two counter-rotating equal discs of vertical axis provided with cutting edges which are tangential to each other along the path of the tobacco filler.
The trimming operation is completed by a rotating brush disposed in proximity to the zone of tangency between the two discs, and on the opposite side to the tobacco filler. The purpose of the rotating brush is to remove from said zone of tangency those tobacco particles which become separated from the filler by the action of the two discs.
The cutting contours of the two trimming discs are normally provided with recesses having their concavity facing the tobacco filler and equidistant from each other, with a pitch equal to the length of one cigarette (again see for example British Pat. No. 881,024). When the trimming discs are correctly phased relative to each other, cutting contours of the aforesaid type generate a tobacco filler in which portions of two different thicknesses alternate.
The portions of greater thickness, generated by the recesses in the two discs meeting each other along the path of the tobacco filler, produce zones of greater tobacco density in the so-called continuous cigarette rod, i.e. after wrapping the filler in the cigarette paper web.
The cutting device operates in these zones to divide the rod into individual cigarettes having a greater tobacco density at their ends than in their middle.
The purpose of these dense portions is to prevent or at least limit the escape of tobacco particles from the ends of the cigarettes during the various processing stages (application of filters, transfer, packaging) to which they are subjected.
From the aforegoing, it follows that the pitch of said zones of greater tobacco density must be changed each time it is necessary to change over from producing cigarettes of one determined length to producing cigarettes of a different length, or in other words when it is required to vary the type of production in a manufacturing machine.
In the described devices of known type, when the trimming discs are replaced by others of a different diameter provided with recesses disposed at the required pitch, it is necessary to move the vertical shafts of the two discs relative to each other in order to restore the condition of tangency between the cutting edges.
This is done by replacing gears in the kinematic chain of the device, and/or by delicate setting operations. In order to avoid said replacements and settings, it is also known to replace the trimmer device completely.
Although advantageous relative to the former by virtue of its practical aspect and speed, this latter system is obviously inconvenient cost-wise.